Distinct Patterns of Auditory Evoked Potentials and Trial-By-Trial Neural Synchrony for Speech and Nonspeech Processing in Children with Autism

Background: Individuals with autism often display atypical auditory evoked potentials (ERP) (Haesen et al., 2011), which could be due to pathological conditions affecting trial-by-trial neural synchrony (David et al., 2016). Such trial-by-trial neural synchrony to the onset of auditory stimulation can be computed as inter-trial coherence (ITC) for different frequency bands of interest. A smaller ITC could be interpreted as representing larger amounts of neural “jitter”. It has been shown that reduced alpha (specifcally at 11.7 Hz) ITC in children with autism may be associated with poorer neuromodulatory control within the sensory cortex (Milne, 2011).

Objectives: This study aimed to verify whether atypical patterns of neural oscillatory activities mediate the auditory evoked responses to speech and non-speech sounds in children with autism.

Methods: EEG data were recorded from school-age Chinese-speaking children with autism and age-matched typically developing (TD) children with a passive listening paradigm. The stimuli were pure tones and Chinese words /bai2/ (Pure tone: ASD N = 15, TD N = 16; Word: ASD N = 14, TD N = 15). Amplitude and latency of P1 and N2 (also known as N250 or delayed N1 in children) components were calculated along with the ITC measures of delta, theta, alpha and beta frequency bands within the windows of interest.

Results: In the pure tone condition, there is a significant N2 reduction accompanied by smaller delta ITCs in the autism group. No group difference in the P1 response were observed. In the word condition, the autism group showed enhanced P1 amplitude accompanied by larger delta, theta, and alpha ITCs. There was a tendency (but not statistically significant) of diminished N2 response. In the pure tone condition, P1/N2 responses in both groups were correlated with ITCs, whereas in the word condition, only the autism group showed such relationship.

Conclusions:  The comparison with age-matched controls in our study revealed distinct patterns of auditory P1/N2 responses and underlying cortical oscillatory activities for speech and nonspeech processing in children with autism. For the pure tone stimuli, we found evidence for weakened perceptual analysis of acoustic features in the N2 component with reduced inter-trial synchrony in the delta band (0~3 Hz) for the autism group. By contrast, we observed enhanced P1 responses to the speech stimuli accompanied by increased neural synchrony in frequency bands of 0 ~ 30 Hz in the autism group, suggesting a hypersensitive reaction to the word onset in children with autism. It remains unclear how these different patterns of neural activities for early sensory processing of speech and nonspeech sounds might correlate with higher-level behavioral perception. Further studies are needed to examine the potential impact of atypical auditory processing on speech and language development in children with autism.